1. Field of the Invention
The present invention relates to a voltage regulator, and more specifically, to a technology of preventing an inrush current at start-up.
2. Description of the Related Art
FIG. 4 is a circuit diagram of a conventional voltage regulator including a circuit for preventing an inrush current at start-up.
The conventional voltage regulator includes an output transistor M1, an on-off control circuit 11, a counter circuit 12, a constant current source Q1 and a resistor R3, which constitute a reference voltage circuit, an error amplifier circuit A1, a short-circuit current limiting circuit MB, an output current limiting circuit MA, a switch 13, and transistors M2 and M3.
The conventional voltage regulator includes a first output current limiting circuit MA1 having a higher current limit value and a second output current limiting circuit MA2 having a lower current limit value, and prevents the inrush current at start-up by operating the second output current limiting circuit MA2 at start-up and switching to the first output current limiting circuit MA1 after a predetermined period of time (see, for example, Japanese Patent Application Laid-open No. 2003-271251).
However, the conventional voltage regulator illustrated in FIG. 4 requires protection circuits having different current limit values and the counter circuit for setting a period in which the inrush current is limited, and therefore has problems of an increased chip area and increased current consumption.